Add clickable watch links to streaming provider badges

Build a provider registry mapping TMDB provider IDs to search URL
templates. `generateProviderUrl()` resolves a URL for a given provider
and title name using URL-encoded search queries. `readAvailability()`
now accepts the title name and attaches `watchUrl` to each offer.

Provider badges with a resolved URL render as `<a>` links opening in a
new tab; tooltip copy switches from the provider name to "Watch on
{name}". Badges without a known URL remain non-interactive as before.

lib/types/title.ts

@@ -20,6 +20,7 @@ export interface AvailabilityOffer {
   providerName: string;
   logoPath: string | null;
   offerType: string;
+  watchUrl: string | null;
 }
 
 export interface RecommendedTitle {